## [Qucs-help] Re: Noise voltage phase

 [Qucs-help] Re: Noise voltage phase From: Stefan Jahn - 2006-05-12 07:51:16 ```Am Do, 11.05.2006, 18:55, schrieb Manley Head: > Hello Stefan; Hi there! > I don't know if my thinking is wrong(quite possible) or if there is a > problem with the Qucs noise handling. > I am trying to measure the phase changes in a simple circuit (attached) > driven by a noise source. > I find that the output contains a (noise) voltage that is not a complex > number as it is when driven by a ac voltage source. > Since it is a real number only then there is no phase information. > This remains the case even when passed through a reactive circuit. > > Why is the noise voltage not a complex number? Is this not a problem > or is my thinking messed up? Hm. As far as I know it is impossible to assign a phase information to a random signal like noise. I think it was hard enough for engineers and mathematicians to assign an amplitude in a certain bandwidth (using some tricks about probability). Michael: Am I wrong? Cheers, Stefan. ```

 [Qucs-help] Re: Noise voltage phase From: Stefan Jahn - 2006-05-12 07:51:16 ```Am Do, 11.05.2006, 18:55, schrieb Manley Head: > Hello Stefan; Hi there! > I don't know if my thinking is wrong(quite possible) or if there is a > problem with the Qucs noise handling. > I am trying to measure the phase changes in a simple circuit (attached) > driven by a noise source. > I find that the output contains a (noise) voltage that is not a complex > number as it is when driven by a ac voltage source. > Since it is a real number only then there is no phase information. > This remains the case even when passed through a reactive circuit. > > Why is the noise voltage not a complex number? Is this not a problem > or is my thinking messed up? Hm. As far as I know it is impossible to assign a phase information to a random signal like noise. I think it was hard enough for engineers and mathematicians to assign an amplitude in a certain bandwidth (using some tricks about probability). Michael: Am I wrong? Cheers, Stefan. ```